In preliminary experiments I have shown that 9-aminoacridine and two anthracycline antibiotics used in the treatment of malignancies, adriamycin and daunorubicin, inhibit differentially DNA polymerases purified from wild-type, mutator, and antimutator T4 bacteriophages. The ratio of polymerase-associated 3' -exonuclease (base removal) to polymerase (base insertion) activities varies significantly for antimutator polymerases as a function of drug concentration. These drug-induced nuclease/polymerase variations are much less significant for wild-type and mutator polymerases. Biochemical and genetic experiments are proposed to study how drug-induced variations in removal and insertion activities effect: (1) incorporation of base analogues and incorrect bases in vitro, (2) mutation frequencies, and (3) recombination frequencies. A detailed theoretical model is presented which will be used to predict spontaneous and base induced mutation frequencies as a function of rates and specificities for base insertion and removal; an equation derived from the model correctly predicts measured incorporation values for the base analogue 2-aminopurine.